Why is the gain of an ideal op-amp considered to be independent of frequency?

Why is the gain of an ideal op-amp considered to be independent of frequency?

• A. We want the op-amp to behave the same way regardless of the input signal frequency
• B. To reduce bandwidth
• C. To increase distortion
• D. To allow the output to saturate less quickly

Answer: (A)

In the ideal op-amp model, the gain is treated as independent of frequency because the device is assumed to have infinite bandwidth. With that assumption, the amplifier can amplify all frequency components equally, so the closed-loop gain is set entirely by the feedback network and remains constant over frequency within the model’s range. The negative feedback forces the output to follow the input by the same proportional ratio regardless of how fast the input signal changes, since the op-amp is considered capable of supplying whatever output is needed without limiting the gain at different frequencies. In real hardware, this is not exact because actual op-amps have finite gain and a finite gain–bandwidth product, which causes the closed-loop gain to eventually roll off at higher frequencies. The other choices describe effects like reducing bandwidth, increasing distortion, or faster saturation, which are not the reason the ideal model treats gain as frequency-invariant.

In the ideal op-amp model, the gain is treated as independent of frequency because the device is assumed to have infinite bandwidth. With that assumption, the amplifier can amplify all frequency components equally, so the closed-loop gain is set entirely by the feedback network and remains constant over frequency within the model’s range. The negative feedback forces the output to follow the input by the same proportional ratio regardless of how fast the input signal changes, since the op-amp is considered capable of supplying whatever output is needed without limiting the gain at different frequencies. In real hardware, this is not exact because actual op-amps have finite gain and a finite gain–bandwidth product, which causes the closed-loop gain to eventually roll off at higher frequencies. The other choices describe effects like reducing bandwidth, increasing distortion, or faster saturation, which are not the reason the ideal model treats gain as frequency-invariant.